Effect of PNF stretching training on the properties of human muscle and tendon structures.
Konrad A, Gad M, and Tilp M. Scand J Med Sci Sports. 2014 [epub ahead of print].
Take Home Message: Following a 6 week proprioceptive neuromuscular facilitation stretching program ankle dorsiflexion was increased and tendon stiffness decreased.
Despite the common use of proprioceptive neuromuscular facilitation (PNF) stretching we have limited information about how it affects range of motion, maximal isometric torque, passive resistive torque, muscle stiffness or tendon stiffness. By better understanding the effect of PNF stretching on musculotendinous performance and structure, clinicians may be able to optimize rehabilitation and pre-participation warm-ups to minimize injury without inhibiting performance. Therefore, Konrad, Gad, and Tilp completed a randomized trial to analyze the effects of a 6-week PNF stretching program on the functional and structural parameter of the ankle joint compared with individuals assigned to a control group. Researchers randomly assigned 49 police cadets (31 male, 18 female) to either a PNF stretching group (25 cadets) or control group (24 cadets). Prior to any intervention, participants’ range of motion (ROM), passive resistive torque, maximum voluntary contraction, and parameters of the muscle and tendon structure (for example, fascicle length, pennation angle, tendon stiffness) were measured. Participants in the PNF group performed a PNF stretching program 5 times per week over a 6 week period. The stretching program consisted of a standing wall stretch of the plantar flexors for 15 seconds, followed by an isometric contraction of the plantar flexors for 6 seconds, and then contract the dorsiflexor muscles for another 15 seconds. This cycle was repeated four times per session. Following the 6-period, the control group had not noticeable changes but the cadets who performed PNF stretching had greater ankle dorsiflexion ROM and pennation angle at rest as well as less active and passive tendon stiffness. Fascicle length, pennation angle in stretching position, passive resistance torque, and maximum voluntary contraction torque did not change among cadets in either group.
Overall, the present study supports the use of PNF stretching as an effective method of increasing dorsiflexion range of motion. Also interesting is the finding that while ankle dorsiflexion increased, the authors only observed changes in the tendon stiffness and pennation angle at rest. This is interesting as it may indicate that while the ROM increases, the muscle may maintain many of its characteristics needed for optimal performance. To better understand the relationship between PNF stretching and its benefits to physical performance, future studies should compare PNF stretching to static and ballistic stretching, as well as measure a more sport-specific movements. Ultimately, this study should aid encourage clinicians in incorporating more PNF stretching into their rehabilitation and conditioning programs.
Questions for Discussion: How often do you prescribe PNF stretching in your rehabilitation or conditioning programs? Have you found PNF stretching to be particularly beneficial to ROM and or overall performance?
Written by: Kyle Harris
Reviewed by: Jeffrey Driban
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Konrad, A., Gad, M., & Tilp, M. (2014). Effect of PNF stretching training on the properties of human muscle and tendon structures Scandinavian Journal of Medicine & Science in Sports DOI: 10.1111/sms.12228